The Wall Street Journal called on special counsel Robert Mueller to excuse himself from his investigation into Russia's interference in the 2016 election.

The paper's editorial board said Monday night that recent news that an FBI agent was dismissed from the investigation because he showed a political bias, along with other circumstances involving Mueller, means he is incapable of fairly pursuing the matter.

"All of this reinforces our doubts about Mr. Mueller’s ability to conduct a fair and credible probe of the FBI’s considerable part in the Russia-Trump drama," the Journal said. "Mr. Mueller ran the bureau for 12 years and is fast friends with [former FBI Director James] Comey, whose firing by Mr. Trump triggered his appointment as special counsel. The reluctance to cooperate with a congressional inquiry compounds doubts related to this clear conflict of interest."

It was reported Saturday Mueller dismissed FBI agent Peter Strzok over the summer from a leading role in the investigation, which is also probing whether President Trump's campaign colluded with Russia. Strzok had apparently sent text messages to a woman he was having an affair with that were critical of Trump.

Republicans and other critics have said the investigation is tainted by partisanship. Trump has called it a "witch hunt."

"The latest news supports our view that Mr. Mueller is too conflicted to investigate the FBI and should step down in favor of someone more credible," said the Journal. "The investigation would surely continue, though perhaps with someone who doesn’t think his job includes protecting the FBI and Mr. Comey from answering questions about their role in the 2016 election."